Grinding mill



0d. 29, 1935. LARSEN 2,019,454

GRINDING MILL Filed Aug. 19, 1932 2 Sheets-Sheet l INVENTOR Oct. 29,1935. LARSEN 2,019,454

GRINDING MILL Filed Aug. 19, 1932 2 Sheets-Sheet 2 46 L L 1 3 11 1L lVIIIIII/IIIIIIII/ (ll KIZIZI SISI.

lNVENTOR Patented Oct. 29, -1935 UNITED STATES PATENT OFFICE Axel NewJersey Application m is,

In Great Britain This invention has been developed with particularreference to the grinding of cement raw material, either in thedrylstate or in the. wet state, but, as will be obvious, it is capable,of adaptation to the grinding of other materials with full realizationof its advantages. The improved mill overcomes disadvantages incidenttothe use of ball mills and tube mills, such as have been used commonlyheretofore in grinding of cement raw materials, in that, in theoperation of the improved mill, it is possible to inspect the grindingoperation at all times and to make from time to time such adjustments asmay be necessary to establish the best workirm conditions. Furthermore,the power consumption is not great as compared with that of ball millsand tube mills, even with heavy charges, and the weight of the mill canbe made considerably less thanthatofa ballmillortubemillofthesamecapacity. As compared with impact pulverizers or hammer mills, in whichthe material is pulverized by the impact of hammers'carried by arotating member the improved mill, by reason of the factthat it can beoperated at a much slower speed, is much less subject to wear and tearand to damage occasioned by especially hard particles.

Furthermore, in the operation of the improved mill the grinding of thematerial is effected by the,

action of the grinding bodies, whether flint pebbles or metal balls orother bodies, which, with the material to be ground, make up the chargeof the mill, the main function of the rotors or stirrers being to effectsuch relative movement of the grinding bodies as will accomplish thegrinding of the material.

The improved mill, in its simplest form, comprises a stationarycontainer or shell which may be open at the top and into which thematerial to be ground is fed at one end and from which the groundmaterial is delivered at the other end, and a disc-like rotor or seriesof disc-like rotors which are rotated about the axis of the;

mill and cause relative rubbing movement without' impact of the grindingbodies with which the mill is charged so that they act by attritionrather than by impact. Provision is made for the passage of the materialoperated upon from the feeding end of the mill to the discharge endwhile the grinding bodies are retained. It will be understood that thedetails of construction ofthemillcanbevariedinmanywaystosuittheconditions'of operation and while several .different embodiments of theinvention are shown and described herein it will be understood thatdiiferent features of construction can be subsmiaui a 00., tierat, N.1., a

signer-tollcorporation meanness! November-23,1381 '4 401m (cue-s)stituted for one another or can be used by themselves or in combinationwith other features, as

the conditions of operation may indicate, and

that, except as pointed out in, the accompanying v claims, the inventionis not restricted'to any particular embodiment.

In the drawings, in which several different embodiments of the inventionare illustrated- Figure 1 is a view, pai-uyin longitudinal section andpartly in elevation, of a mill which embodies lo the invention.

Figure 2 is a view of the same as'seen from above.

Figure 3 is a vlewin transverse section, on the plane indicated by thebroken line 3-3 of Figures 5 1 and 2, showing particularly the preferredconstruction of eachof the rotor discs.

Figure 4 is a transverse section on the plane indicated by the brokenlinel-l of Figures 1 and 2 illustrating particularly the preferredconstrucgo tionof eachofthepartitionsintermediate the rotor discs. 7 a

FigureSisa viewslmilartoFigure 1 butshowing the rotor discs ofprogressively increasing and the shell as conformed thereto.

Figured is a view in elevation of a rotor in the form of a cage, theintermediate partitions being 11 omitted.

Figures 7 and 8 are detail views, respectively in section and inelevation, illustrating a device for the control of the movement of thematerial being ground.

Figure 9 isa view similar to Figure 1, but

showing the rotors arranged in groups with a In the embodiment of theinvention shown in Figures 1-4 the stationary non-rotating shell orcasing or container I, whichmay be made of steel platesand conformgenerally, in its lower portion,totherotordiscstohereferredto,and

having ariopentomisshownasmounted ona suitahlebase llanda'sreceivingaxiallyashaftso 2onwhicharemounted,soastorotatetherewith,discs 3, provided with suitable perforations I. The shaft, 2 may berotated by any suitable means, as, for example, thro h a gear 5, apinion ,and'abandpulley 8 keyed on the shaft I of the pinion. Suitablebearings may be provided at I for the shaft 2 and at IQ for the drivingshaft I. All of these parts may be supported in any suitable manner ason the base or foundation I I. Suitable packing boxes, as at l2, may beprovided in the ends of the shell I for the shaft 2.

In this embodiment of the invention there is provided for each disc 3and in the same plane therewith a diaphragm or partition it which fitsabout theperiphery of the disc with a slight clearance, these diaphragmsl3 being otherwise imperforate and closing the space between each discand the casing so that the grinding bodies are held back and all of thematerial being ground is compelled to pass through the perforations ofthe disc on,its way to the discharge end of the casing. Intermediate thediscs 3 with their diaphragms l3 are partitions ll, which may partiallyencircle the shaft 2 and the hubs of the discs 3 and are formed withperforations. as at M.

The stationary non-rotating shell may be provided, as at IS, with a feedhopper and near the other end with a screen It which permits the finelyground material to pw' through it while retaining the grinding bodiesand insufliciently ground material, such finely ground material beingdelivered through a spout [1 into a suitable transport device not shown.For the purpose of controlling the discharge of the finely groundmaterial the screen, as shown in Figures TI and 8, may be formed of twoperforated plates l6 and I6, one of which may be shifted with respect tothe other so as to vary the area of the opening 18 through which thematerial is permitted to pass.

In the operation of the mill shown in Figures 1-4 it being assumed thatthe mill has been charged with grinding bodies, as indicated at It inFigure l, and that the rotors have been set in motion, the material tobe ground is fed continuously into the mill, entering the chamber formedbetween the end of the shell and the first rotor. The grinding bodiesand the material in each compartment between successive rotor discs areheld back by the imperforatepartitions l3, the grinding bodies beingalso retained by the intermediate partitions ll. By the action'of therotor discs the grinding bodies adjacent the discs will have a relativerubbing motion imparted to them and act upon the material by attritionrather than by impact while the grinding bodies adjacent the stationarypartitions II will have less relativetmovement. It will be understood,however, that the grinding bodies may be con stantly changing theirpositions between each rotor disc and the adjacent stationary partition.By reason of the relative rubbing movement of thegrindingbodiesthusestablishedthematerial to be g ound. which fills the interstitialspacesbetweenthegrindingbodies,willbe ground between the faces ofadjacent grinding bodiesandalsobetweenthefacesofthegrind ing bodiesandthe faces of theadiacent partitions and rotor discs and such groundmaterial willpassthroughtheperforationsloftherotordiscsIandalsothroughtheperforationsllof the partitions I, beingprogressively reduced in finenesuntiltheilnely groundmaterial canpassthroughthescreen'lt andsobe discharged from the. mill. The normal rateof rotation of the'shaftlandtherotordisclwiilbecomparativelyslow'andastheprolrellofthegrindlilcan beobservedfromthetopofthemilhitisasimple the material passedoutside the disc 3 alon titions ll of Figure matter to vary the rate ofrotation'to .produce the desired result.

It will be understood that the partitions l3, closely encircling thediscs 3, serve to prevent jamming of the grinding bodies between theedges of the discs 3 and the wall of the mill and serve alsoto compelthe material to pass through the apertures of the discs 3 and so obtaina greater grinding effect than would be possible if the 10 wall of themillv While the shell or wall of the container may be conveniently madeof steel plates it will be understood that it might be made=of concrete,for example, for the wear on the wall of the mill is slight, as it isprotected by grinding bodies. which have litle or no motion. The rotordiscs 3 and the partitions ll should be made of a highly wear resistantmaterial in order to withstand the action of the grinding bodies and forthe samereason the rotor discs 3 should be pro- 1 vided with long hubsto cover completely the shaft 2.

It will be understoodthat if the operation of the mill be started whenfully charged the re- 28 sistance offered by the perforated rotor discsto the moment of starting will be considerable because of the pressureof the grinding bodies and material against the discs. This difllcultymay be overcome by provision of shown in Figure 10, one of which may beslipped in place in front of each rotor disc when the mill is empty ornearly empty to protect each disc from the pressure of the grindingbodies and material and so reduce the resistance of the mill asto thestarting moment. When-the starting re- .sistance has been overcome the-plates can be withdrawn.

As another means of reducing resistance .to the starting moment eachrotor disc 3*, as shownin b Figure 11, can be connected to the shaft 2through the medium of a spiral spring 3 so that the rotation of theshaft maybe started readily and movement imparted gradually to each ofthe discs. 4.6 In the embodiment of the invention shown in Figure 1 thediscs 3 are of the same diameter and the lower part of the shell of themill is cylindrical to conform therewith. If it should be desired eitherto promote or retard the passage of the material through the mill thediscs 3 might be made of successively different diameters, as shown inFigure 5, the shell I being 4 conformed thereto and the partitions l3and I being shaped accordingly. In other respects the construction ofthe mill illustrated in Figure 5 may be the same. as that illustrated inFigure 1. I

It is obvious that with the partitions l4 omitted the several rotordiscs 3 might be united go by bars 3' and stay bolts 3 to form acage-like structure as illustrated in Figure 6, mounted on the shaft 2to be rotated therewith. Except for I the function performed by theperforated par- 1 the operation 017 a mill '5 equipped with such acage-like structure is the same as that already described with respectto 'Figure 1, the material as it is ground passing through the openingsof the discs 3 while the grinding action is accomplished by the relativemovement of the grinding bodies between the discs I.

ii are shown as arranged ingroups, with .8 P Ti slotted plates I9, 30-

forated partition I 4 between successive groups. The operation or such amill will be readily understood without further explanation.

I claim as my invention: 7

1. In a grinding mill, the combination of a stationary, non-rotatingshell adapted to receive a charge of grinding bodies and material to beground and to discharge the ground material, a perforated rotor disc toefiect relative movement of the grinding bodies, means to rotate therotor, and a partition encircling the rotor in the plane thereof andclosing the space between-the rotor and the fixed shell.

2. In a grinding mill, the combination of a stationary, non-rotatingshell adapted to receive, a charge of grinding bodies and material to beground and to discharge the ground material, a plurality of rotors toeffect relative movement of the grinding bodies, perforated partitionsinterposed between the rotors, fixed imperforate partitions encirclingthe rotors in the plane thereof and closing the space between the sameand the shell, and means to rotate the rotors.

3. In a grinding mill, the combination of a stationary, non-rotatingshe-.1 mounted on a relative rubbing movement of the grinding bodies 5without impact, means to rotate the rotor, and

a screen at the discharge end of the shell to permit the discharge ofthe flnelyground material and to retain the grinding bodies and coarselyground material. l0 4. In a grinding mill, the combination of astationary,non-rotating shell with a horizontal axis adapted to receivea charge of grinding bodies and material to be ground and to dischargethe ground material, a perforated rotor disc 15 mounted on a horizontalaxis to eflect relative rubbing movement of the grinding bodies withoutimpact, means to rotate the rotor, a screen at the discharge end of theshell to permit the discharge oi the finely ground material and to 20retain the grinding bodies and coarsely ground material, and means toregulate the discharge of the material through said screen.

am LARSEN. 25

